Digital-analog converters of this type are used in particular in mobile radiotelephone base stations in order to convert digital data having a high bit rate into high-frequency transmission signals. In this situation, the high-frequency transmission signals are to be generated with a high level of spectral purity, in other words they should exhibit as few unwanted spurious frequencies as possible. Moreover, this should be achieved cost-effectively with the smallest possible demand on technical resources. In the typical case, the high-frequency transmission signals should have one or more modulated frequency carriers and be capable of covering a large bandwidth.
To date, architectures have been employed for this purpose which use known digital-analog converters to generate high-bandwidth analog signals in a frequency range which is too low for transmission. Subsequently, the analog signals are then converted by one or two frequency converter stages, for example mixer stages, into the high-frequency transmission signals in order to be sent by radio from the mobile radiotelephone base station.
The mixer stages, however, require a high level of resources in terms of circuitry, in particular a high demand for electronic components. In general, the mixer stages cannot be implemented as integrated circuits since filters having a high quality level must be used and, as is known, these require a large number of passive components such as capacitors and resistors. Passive components cannot however be conveniently implemented in integrated circuits, particularly when precise and in part high capacitance and/or inductance values are required for high-quality filters. Furthermore, all intermediate frequencies must be screened off separately. In order to provide a cost-effective and thus economical solution, a digital-analog converter would therefore be required which comprises a small number of electronic components, passive components in particular, and is preferably suitable for implementation as an integrated circuit.